Oxaliplatin-Induced Senescence in Colorectal Cancer Cells Depends on p14ARF-Mediated Sustained p53 Activation

Maja T Tomicic,Christian Schwarzenbach,Markus Christmann,Franziska Krämer,Alexandra Nguyen

doi:10.3390/cancers13092019

Abstract

Simple SummaryChemotherapy can lead to cellular senescence in tumor cells. Here we demonstrate that oxaliplatin induces senescence in p53-proficient colorectal cancer (CRC) cells and leads to the G2-phase arrest in all lines studied (HCT116p53+/+, HCT116p53−/−, LoVo, SW48, and SW480). At early times the p53-competent lines activate p53 and p21CIP1, however, at later times, only LoVo cells showed sustained p53/p21CIP1 activation, accompanied by a strong induction of senescence and senescence-associated secretory phenotype (SASP) factors. Opposite to LoVo, the p53/p21CIP1 response and senescence induction is much weaker in the other p53-proficient cells, due to p14ARF deficiency. LoVo cells express p14ARF protein and siRNA-mediated knockdown of p14ARF significantly reduces sustained p53/p21CIP1 activation and senescence. Vice versa, ectopic expression of p14ARF enhances oxaliplatin-induced senescence in SW48 and SW480 cells. Our data show that oxaliplatin-induced senescence in CRC cells depends on p53 proficiency; however, a significant induction can only be observed upon p14ARF-mediated p53 stabilization.Senescence is an important consequence of cytostatic drug-based tumor therapy. Here we analyzed to which degree the anticancer drug oxaliplatin induces cell death, cell cycle arrest, and senescence in colorectal cancer (CRC) cells and elucidated the role of p53. Oxaliplatin treatment resulted in the G2-phase arrest in all CRC lines tested (HCT116p53+/+, HCT116p53−/−, LoVo, SW48 and SW480). Immunoblot analysis showed that within the p53-competent lines p53 and p21CIP1 are activated at early times upon oxaliplatin treatment. However, at later times, only LoVo cells showed sustained activation of the p53/p21CIP1 pathway, accompanied by a strong induction of senescence as measured by senescence-associated β-Gal staining and induction of senescence-associated secretory phenotype (SASP) factors. Opposite to LoVo, the p53/p21CIP1 response and senescence induction was much weaker in the p53-proficient SW48 and SW480 cells, which was due to deficiency for p14ARF. Thus, among lines studied only LoVo express p14ARF protein and siRNA-mediated knockdown of p14ARF significantly reduced sustained p53/p21CIP1 activation and senescence. Vice versa, ectopic p14ARF expression enhanced oxaliplatin-induced senescence in SW48 and SW480 cells. Our data show that oxaliplatin-induced senescence in CRC cells is dependent on p53 proficiency; however, a significant induction can only be observed upon p14ARF-mediated p53 stabilization.

Highlights

The same level of toxicity was achieved in HCT116p53+/+ and SW480 cells upon exposure to 5 μM, as well as in SW48 cells after treatment with 10 μM oxaliplatin
Similar to the phosphorylation of p53 and induction of p21CIP1, a significantly enhanced frequency of senescence was only observed in p14ARF expressing SW48 and SW480 cells after oxaliplatin treatment (Figure 7D)
SW48 and SW480 cells, the cells were transiently transfected with a p14ARF expression plasmid [14] (Figure 7C)

Summary

Introduction

Telomeres are constantly shortened and can be recognized as DSBs, whereas during oncogenic senescence, mutations in oncogenes lead to the activation of positive cell cycle regulators, driving cells into excessive ori firing and re-replication, and via breakdown of the replication forks to the formation of DSBs. In all circumstances, the unrepaired DSBs trigger a chronic activation of the DDR and via ATR/ATM signaling induction of p53 and CDKN1A/p21CIP1 , eventually inducing senescence (for review see [6,7]). Besides p21CIP1 , two additional factors are important for senescence induction and maintenance, namely p14ARF and p16INK4A [10,11]. Both factors are transcribed from the CDKN2A gene. Whereas p16INK4a inhibits CDK4 and CDK6 [12], p14ARF acts as a stabilizer for p53, as it can sequester MDM2, a protein responsible for the degradation of p53 [13,14,15]

Methods

Results

Conclusion